As one of the methods for synthesizing liquid fuels from a natural gas, a GTL (Gas To Liquids: liquid fuel synthesis) technique of reforming a natural gas to produce a synthesis gas containing a carbon monoxide gas (CO) and a hydrogen gas (H2) as the main components, synthesizing hydrocarbons using this synthesis gas as a source gas by the Fischer-Tropsch synthesis reaction (hereinafter, in some cases, referred to as “FT synthesis reaction”), and further hydrogenating and refining the hydrocarbons to produce liquid fuel products, such as naphtha (raw gasoline), kerosene, gas oil, and wax, has recently been developed.
Here, since the liquid fuel products obtained from the FT synthesis hydrocarbons obtained by the FT synthesis reaction as a feedstock have high paraffin content, and hardly include any sulfur components as shown, for example, in Patent Document 1, they have been paid attention to as a fuel which is compatible with the environment.
Further, the FT synthesis hydrocarbons supplied to a fractionator, for example, as shown in Patent Document 2, are fractionally distilled according to boiling points, and the fractionally distilled hydrocarbons are then obtained from discharge ports respectively provided at the upper part, middle part, and lower part of the fractionator.